AGIPD, the Adaptive Gain Integrating Pixel Detector, is a hybrid detector with a frame rate of 4.5 MHz, a dynamic range up to 104⋅ 12.4 keV photons, as well as single photon resolution, developed for the European XFEL (Eu.XFEL). The final 1 Mpixel detector system consists of 16 tiled modules each one with 16 readout chips. The single ASIC is 64 x 64 pixels, each with a size of 200 x 200 μm2. Each pixel can store up to 352 images. This work is focused on the characterization of AGIPD1.1, the second version of the full scale ASIC, and the improvements with respect to AGIPD1.0. From the measurements presented in this paper we show that the flaws observed in AGIPD1.0 (i.e. ghosting, crosstalk, slow readout speed) have been fixed in AGIPD1.1. In addition the main performance parameters such as noise, dynamic range and so on were measured for the new version of the ASIC and will be summarized. 

The European XFEL is an extremely brilliant Free Electron Laser Source with a very demanding pulse structure: trains of 2700 X-ray pulses are repeated at 10Hz. The pulses inside the train are spaced by 220ns and each one contains up to 1012photons of 12.4keV, while being ≤100fs in length. AGIPD, the Adaptive Gain Integrating Pixel Detector, is a hybrid pixel detector developed by DESY, PSI, and the Universities of Bonn and Hamburg to cope with these properties. It is a fast, low noise integrating detector, with single photon sensitivity (for Eγ⪆6keV) and a large dynamic range, up to 104 photons at 12.4keV. This is achieved with a charge sensitive amplifier with 3 adaptively selected gains per pixel. 352 images can be recorded at up to 6.5MHz and stored in the in-pixel analogue memory and read out between pulse trains. The core component of this detector is the AGIPD ASIC, which consists of 64 × 64 pixels of 200µm×200µm. Control of the ASIC's image acquisition and analogue readout is via a command based interface. FPGA based electronic boards, controlling ASIC operation, image digitisation and 10GE data transmission interface AGIPD detectors to DAQ and control systems. An AGIPD 1Mpixel detector has been installed at the SPB1 experimental station in August 2017, while a second one is currently commissioned for the MID 2 endstation. A larger (4Mpixel) AGIPD detector and one to employ Hi-Z sensor material to efficiently register photons up to Eγ≈25keV are currently under construction. 

In this paper, we are presenting the Percival detector, a monolithic CMOS Imager for detection of soft x-rays in Synchrotron Rings and Free Electron Lasers. The imager consists in a 2D array of many (2M) small (27um pitch) pixels, without dead or blind zones in the imaging area. The imager achieves low noise and high dynamic range by means of an adaptive-gain in-pixel circuitry, that has been validated on prototypes. The imager features on-chip Analogue-to-Digital conversion to 12+1 bits, and has a readout speed which is compatible with most of Free Electron Laser Facilities. For direct detection of low-energy x-rays, the imager is back-illuminated and post-processed to achieve 100% fill factor. 

The Adaptive Gain Integrating Pixel Detector (AGIPD) is an X-ray imager, custom designed for the European X-ray Free-Electron Laser (XFEL). It is a fast, low-noise integrating detector, with an adaptive gain amplifier per pixel. This has an equivalent noise of less than 1keV when detecting single photons and, when switched into another gain state, a dynamic range of more than 10(4)photons of 12keV. In burst mode the system is able to store 352 images while running at up to 6.5MHz, which is compatible with the 4.5MHz frame rate at the European XFEL. The AGIPD system was installed and commissioned in August 2017, and successfully used for the first experiments at the Single Particles, Clusters and Biomolecules (SPB) experimental station at the European XFEL since September 2017. This paper describes the principal components and performance parameters of the system.

The peak brilliance reached by today's Free-Electron Laser and Synchrotron light sources requires photon detectors matching their output intensity and other characteristics in order to fully realize the sources' potential. The Pixellated Energy Resolving CMOS Imager, Versatile And Large (Percival) is a dedicated soft X-ray imager (0.25-1 keV) developed for this purpose by a collaboration of DESY, Rutherford Appleton Laboratory/STFC, Elettra Sincrotrone Trieste, Diamond Light Source, and Pohang Accelerator Laboratory. Following several generations of prototypes, the Percival "P2M" 2-Megapixel imager - a 4.5x5 cm monolithic, stitched sensor with an uninterrupted imaging area of 4x4 cm(2) (1408x1484 pixels of 27x27 mu m - was produced and has demonstrated basic functionality with a first-light image using visible light. It is currently being brought to full operation in a front-illuminated configuration. The readout system being commissioned in parallel has been developed specifically for this imager which will produce - at full 300 Hz frame rate - data at 20 Gbit/s. A first wafer with eight Percival P2M chips has undergone backthinning to enable soft X-ray detection. It has been diced and chips are currently being wirebonded. We summarize here the P2M system, the project status, and show the P2M sensor's first response to visible light.

Synchrotrons can provide very intense and focused X-ray beams, which can be used to study the structure of matter down to the atomic scale. In many experiments, the quality of the results depends strongly on detector performance; in particular, experiments studying dynamics of samples require fast, sensitive X-ray detectors. "LAMBDA" is a photon-counting hybrid pixel detector system for experiments at synchrotrons, based on the Medipix3 readout chip. Its main features are a combination of comparatively small pixel size (55 μm), high readout speed at up to 2000 frames per second with no time gap between images, a large tileable module design, and compatibility with high-Z sensors for efficient detection of higher X-ray energies. A large LAMBDA system for hard X-ray detection has been built using Cr-compensated GaAs as a sensor material. The system is composed of 6 GaAs tiles, each of 768 by 512 pixels, giving a system with approximately 2 megapixels and an area of 8.5 by 8.5 cm2. While the sensor uniformity of GaAs is not as high as that of silicon, its behaviour is stable over time, and it is possible to correct nonuniformities effectively by postprocessing of images. By using multiple 10 Gigabit Ethernet data links, the system can be read out at the full speed of 2000 frames per second. The system has been used in hard X-ray diffraction experiments studying the structure of samples under extreme pressure in diamond anvil cells. These experiments can provide insight into geological processes. Thanks to the combination of high speed readout, large area and high sensitivity to hard X-rays, it is possible to obtain previously unattainable information in these experiments about atomic-scale structure on a millisecond timescale during rapid changes of pressure or temperature. 

The new European X-ray Free-Electron Laser is the first X-ray free-electron laser capable of delivering X-ray pulses with a megahertz inter-pulse spacing, more than four orders of magnitude higher than previously possible. However, to date, it has been unclear whether it would indeed be possible to measure high-quality diffraction data at megahertz pulse repetition rates. Here, we show that high-quality structures can indeed be obtained using currently available operating conditions at the European XFEL. We present two complete data sets, one from the well-known model system lysozyme and the other from a so far unknown complex of a beta-lactamase from K. pneumoniae involved in antibiotic resistance. This result opens up megahertz serial femtosecond crystallography (SFX) as a tool for reliable structure determination, substrate screening and the efficient measurement of the evolution and dynamics of molecular structures using megahertz repetition rate pulses available at this new class of X-ray laser source.

AGIPD is a hybrid pixel detector developed by DESY, PSI, and the Universities of Bonn and Hamburg. It is targeted for use at the European XFEL, a source with unique properties: a train of up to 2700 pulses is repeated at 10 Hz rate. The pulses inside a train are ≤100fs long and separated by 220 ns, containing up to 1012 photons of 12.4 keV each. The readout ASICs with 64 x 64 pixels each have to cope with these properties: Single photon sensitivity and a dynamic range up to 104 photons/pixel in the same image as well as storage for as many as possible images of a pulse train for delayed readout, prior to the next train. The high impinging photon flux also requires a very radiation hard design of sensor and ASIC, which uses 130 nm CMOS technology and radiation tolerant techniques. The signal path inside a pixel of the ASIC consists of a charge sensitive preamplifier with 3 individual gains, adaptively selected by a subsequent discriminator. The preamp also feeds to a correlated double sampling stage, which writes to an analogue memory to record 352 frames. It is random-access, so it can be used most efficiently by overwriting bad or empty images. Encoded gain information is stored to a similar memory. Readout of these memories is via a common charge sensitive amplifier in each pixel, and multiplexers on four differential ports. Operation of the ASIC is controlled via a command interface, using 3 LVDS lines. It also serves to configure the chip's operational parameters and timings.

Here we present new result on the testing of a Germanium sensor for X-ray radiation. The system is made of 3 × 2 Medipix3RX chips, bump-bonded to a monolithic sensor, and is called "hexa". Its dimensions are 45 × 30 mm2 and the sensor thickness was 1.5 mm. The total number of the pixels is 393216 in the matrix 768 × 512 with pixel pitch 55 μ m. Medipix3RX read-out chip provides photon counting read-out with single photon sensitivity. The sensor is cooled to -126°C and noise levels together with flat field response are measured. For -200 V polarization bias, leakage current was 4.4 mA (3.2 μ A/mm2). Due to higher leakage around 2.5% of all pixels stay non-responsive. More than 99% of all pixels are bump bonded correctly. In this paper we present the experimental set-up, threshold equalization procedure, image acquisition and the technique for bump bond quality estimate.

The development of new materials and improvements of existing ones are at the root of the spectacular recent developments of new technologies for synchrotron storage rings and free-electron laser sources. This holds true for all relevant application areas, from electron guns to undulators, x-ray optics, and detectors. As demand grows for more powerful and efficient light sources, efficient optics, and high-speed detectors, an overview of ongoing materials research for these applications is timely. In this article, we focus on the most exciting and demanding areas of materials research and development for synchrotron radiation optics and detectors. Materials issues of components for synchrotron and free-electron laser accelerators are briefly discussed. The articles in this issue expand on these topics.